PHP : XML Create-Add-Edit-Modify using DOM, SimpleXML, XPath

Written on September 4, 2010
Estimated reading time : 21 mins
Tags : | php | xml |

Note :

This is an old popular post from my personal blog. I moved it here so as to get all my technical content together.


Over the last few working days, I spent a quite a bit of time playing around with XML. While searching through the net, I found few comprehensive PHP XML guides. There never was a ‘1 stop all operations’ guide for learning XML.

As such I decided to club together examples of all kinds of operations I ever did on XML in a single post. I hope it benefits others out there who wish to learn more about XML manipulation.

Note : Since the post got quite large, I decided to only use the Tree Map style parsers – DOM & Simple XML.

"XML"

Operations Performed

  1. Create XML OR Array to XML Conversion OR CDATA Element
  2. Edit XML – Edit/Modify Element Data (accessed serially)
  3. Edit XML – Edit specific Elements (accessed conditionally)
  4. Edit XML – Element Addition (to queue end)
  5. Edit XML – Element Addition (to queue start)
  6. Edit XML – Element Addition (before a specific node)
  7. Delete Elements (accessed serially)
  8. Delete Elements (accessed conditionally)
  9. Rearrange / Reorder Elements
  10. Display Required data in XML Form itself OR Remove all children nodes save one OR Copy/Clone Node Eg OR Compare/Search non numeric data (like date or time) to get result.

Following content from library.xml will be used in all operations :

<?xml version="1.0"?>
<library>
  <book isbn="1001" pubdate="1943-01-01">
    <title><![CDATA[The Fountainhead]]></title>
    <author>Ayn Rand</author>
    <price>300</price>
  </book>
  <book isbn="1002" pubdate="1954-01-01">
    <title><![CDATA[The Lord of the Rings]]></title>
    <author>J.R.R.Tolkein</author>
    <price>500</price>
  </book>
  <book isbn="1003" pubdate="1982-01-01">
    <title><![CDATA[The Dark Tower]]></title>
    <author>Stephen King</author>
    <price>200</price>
  </book>
</library>

1. Create XML OR Array to XML Conversion OR CDATA Element

SimpleXML :

// Cant create CDATA element for title in SimpleXML.
function fnSimpleXMLCreate() {
    $arr = array(array('isbn'=>'1001', 'pubdate'=>'1943-01-01', 'title'=>'The Fountainhead',
                            'author'=>'Ayn Rand', 'price'=>'300'),
                        array('isbn'=>'1002', 'pubdate'=>'1954-01-01',
                            'title'=>'The Lord of the Rings', 'author'=>'J.R.R.Tolkein',
                            'price'=>'500'),
                        array('isbn'=>'1003', 'pubdate'=>'1982-01-01', 'title'=>'The Dark Tower',
                            'author'=>'Stephen King', 'price'=>'200'));
        
    $library = new SimpleXMLElement('<library />');
        
    for($i = 0; $i < 3; $i++) {
        $book = $library->addChild('book');
        $book->addAttribute('isbn', $arr[$i]['isbn']);
        $book->addAttribute('pubdate', $arr[$i]['pubdate']);
        $book->addChild('title', $arr[$i]['title']); //cant create CDATA in SimpleXML.
        $book->addChild('author', $arr[$i]['author']);
        $book->addChild('price', $arr[$i]['price']);
    }
    
    // header("Content-type: text/xml");
    // echo $library->asXML();
    $library->asXML('library.xml');
}

DOM :

function fnDomCreate() {
    $arr = array(array('isbn'=>'1001', 'pubdate'=>'1943-01-01', 'title'=>'The Fountainhead',
                            'author'=>'Ayn Rand', 'price'=>'300'),
                        array('isbn'=>'1002', 'pubdate'=>'1954-01-01',
                            'title'=>'The Lord of the Rings', 'author'=>'J.R.R.Tolkein',
                            'price'=>'500'),
                        array('isbn'=>'1003', 'pubdate'=>'1982-01-01', 'title'=>'The Dark Tower',
                            'author'=>'Stephen King', 'price'=>'200'));
        
    $dom = new DOMDocument();
    $library = $dom->createElement('library');
    $dom->appendChild($library);
        
    for($i = 0; $i < 3; $i++) {
        $book = $dom->createElement('book');
        $book->setAttribute('isbn',$arr[$i]['isbn']);
            $book->setAttribute('pubdate',$arr[$i]['pubdate']);
            
        //$prop = $dom->createElement('title', $arr[$i]['title']);
        $prop = $dom->createElement('title');
        $text = $dom->createCDATASection($arr[$i]['title']);
        $prop->appendChild($text);
        $book->appendChild($prop);
            
        $prop = $dom->createElement('author', $arr[$i]['author']);
        $book->appendChild($prop);
        $prop = $dom->createElement('price', $arr[$i]['price']);
        $book->appendChild($prop);
        $library->appendChild($book);
    }
    //header("Content-type: text/xml");
    $dom->save('library.xml');
}

2. Edit XML – Edit/Modify Element Data (accessed serially)

SimpleXML :

// Edit Last Book Title
function fnSimpleXMLEditElementSeq() {
    $library = new SimpleXMLElement('library.xml',null,true);
    $num = count($library);
    $library->book[$num-1]->title .= ' - The Gunslinger';
    // header("Content-type: text/xml");
    // echo $library->asXML();
    $library->asXML('library_modified.xml');
}

DOM :

// Edit Last Book Title
function fnDOMEditElementSeq() {
    $dom = new DOMDocument();
    $dom->load('library.xml');
    $library = $dom->documentElement;
    $cnt = $library->childNodes->length;
        
    $library->childNodes->item($cnt-1)->getElementsByTagName('title')->item(0)->nodeValue .= ' Series'; 
    // 2nd way #$library->getElementsByTagName('book')->item($cnt-1)->getElementsByTagName('title')->item(0)->nodeValue .= ' Series';
    
    // 3rd Way
    // $library->childNodes->item($cnt-1)->childNodes->item(0)->nodeValue .= ' Series';
    //header("Content-type: text/xml");
    $dom->save('library_modified.xml');
}

3. Edit XML – Edit specific Elements (accessed conditionally)

SimpleXML :

// Edit Title of book with author J.R.R.Tolkein
function fnSimpleXMLEditElementCond() {
    $library = new SimpleXMLElement('library.xml',null,true);
    $book = $library->xpath('/library/book[author="J.R.R.Tolkein"]');
    $book[0]->title .= ' Series';
    // header("Content-type: text/xml");
    // echo $library->asXML();
    $library->asXML('library_modified.xml');
}

DOM :

// Edit Title of book with author J.R.R.Tolkein
function fnDOMEditElementCond() {
    $dom = new DOMDocument();
    $dom->load('library.xml');
    $library = $dom->documentElement;
    $xpath = new DOMXPath($dom);
    $result = $xpath->query('/library/book[author="J.R.R.Tolkein"]/title');
    $result->item(0)->nodeValue .= ' Series';
    // This will remove the CDATA property of the element.
    // To retain it, delete this element (see delete eg) & recreate it with CDATA (see create xml eg).
    
    // 2nd Way
    // $result = $xpath->query('/library/book[author="J.R.R.Tolkein"]');
    // $result->item(0)->getElementsByTagName('title')->item(0)->nodeValue .= ' Series';
    //header("Content-type: text/xml");
    $dom->save('library_modified.xml');
}

4. Edit XML – Element Addition (to queue end)

SimpleXML :

// Add another Book to the end
function fnSimpleXMLAddElement2End() {
    $library = new SimpleXMLElement('library.xml',null,true);
    $book = $library->addChild('book');
    $book->addAttribute('isbn', '1004');
    $book->addAttribute('pubdate', '1960-07-11');
    $book->addChild('title', "To Kill a Mockingbird");
    $book->addChild('author', "Harper Lee");
    $book->addChild('price', "100");
    // header("Content-type: text/xml");
    // echo $library->asXML();
    $library->asXML('library_modified.xml');
}

DOM :

// Add another Book to the end
function fnDOMAddElement2End() {
    $dom = new DOMDocument();
    $dom->load('library.xml');
    $library = $dom->documentElement;
     
    $book = $dom->createElement('book');
    $book->setAttribute('isbn', '1000');
    $book->setAttribute('pubdate','1960-07-11');
     
    $prop = $dom->createElement('title');
    $text = $dom->createTextNode('To Kill a Mockingbird');
    $prop->appendChild($text);
    $book->appendChild($prop);
     
    $prop = $dom->createElement('author', 'Harper Lee');
    $book->appendChild($prop);
    $prop = $dom->createElement('price', '100');
    $book->appendChild($prop);
     
    $library->appendChild($book);
    //header("Content-type: text/xml");
    $dom->save('library_modified.xml');
}

5. Edit XML – Element Addition (to queue start)

SimpleXML :

// Add a Book to List Start
// Insert Before Functionality not present in SimpleXML 
// We can integrate DOM with SimpleXML to do it.
function fnSimpleXMLAddElement2Start() {
    $libSimple = new SimpleXMLElement('library.xml',null,true);
    $libDom = dom_import_simplexml($libSimple);
        
    $dom = new DOMDocument();
    //returns a copy of the node to import
    $libDom = $dom->importNode($libDom, true);
    //associate it with the current document.
    $dom->appendChild($libDom);
        
    fnDOMAddElement2Start($dom); //see below DOM function
}

DOM :

function fnDOMAddElement2Start($dom='') {
    if (!$dom) {
        $dom = new DOMDocument();
        $dom->load('library.xml');
    }
    $library = $dom->documentElement;
    #var_dump($library->childNodes->item(0)->parentNode->nodeName);
    $book = $dom->createElement('book');
    $book->setAttribute('isbn', '1000');
    $book->setAttribute('pubdate', '1960-07-11');
        
    $prop = $dom->createElement('title', 'To Kill a Mockingbird');
    $book->appendChild($prop);
    $prop = $dom->createElement('author', 'Harper Lee');
    $book->appendChild($prop);
    $prop = $dom->createElement('price', '100');
    $book->appendChild($prop);
        
    $library->childNodes->item(0)->parentNode->insertBefore($book, $library->childNodes->item(0));
    //header("Content-type: text/xml");
    $dom->save('library_modified.xml');
}

6. Edit XML – Element Addition (before a specific node)

SimpleXML :

// Add a Book Before attribute isbn 1002
// Insert Before Functionality not present in SimpleXML 
// We can integrate DOM with SimpleXML to do it.
function fnSimpleXMLAddElementCond() {
    $libSimple = new SimpleXMLElement('library.xml', null, true);
    $libDom = dom_import_simplexml($libSimple);
        
    $dom = new DOMDocument();
    //returns a copy of the node to import
    $libDom = $dom->importNode($libDom, true);
    //associate it with the current document.
    $dom->appendChild($libDom);
        
    fnDOMAddElementCond($dom); //see below DOM eg.
}

DOM :

// Add a Book Before isbn 1002
function fnDOMAddElementCond($dom='')
{
    if(!$dom) {
        $dom = new DOMDocument();
        $dom->load('library.xml');
    }
    $library = $dom->documentElement;
        
    $book = $dom->createElement('book');
    $book->setAttribute('isbn','1000');
    $book->setAttribute('pubdate', '1960-07-11');
        
    $prop = $dom->createElement('title', 'To Kill a Mockingbird');
    $book->appendChild($prop);
    $prop = $dom->createElement('author', 'Harper Lee');
    $book->appendChild($prop);
    $prop = $dom->createElement('price', '100');
    $book->appendChild($prop);
        
    $xpath = new DOMXPath($dom);
    $result = $xpath->query('/library/book[@isbn="1002"]');
    $library->childNodes->item(0)->parentNode->insertBefore($book,$result->item(0));
    //header("Content-type: text/xml");
    $dom->save('library_modified.xml');
}

7. Delete Elements (accessed serially)

SimpleXML :

// Delete 2nd book
function fnSimpleXMLDeleteSeq() {
    $library = new SimpleXMLElement('library.xml', null, true);
    //$library->book[1] = null; // this only empties content
    unset($library->book[1]);
    // header("Content-type: text/xml");
    // echo $library->asXML();
    $library->asXML('library_modified.xml');
}

DOM :

// Delete 2nd Book
function fnDOMDeleteSeq() {
    $dom = new DOMDocument();
    $dom->load('library.xml');
    $library = $dom->documentElement;
        
    $library->childNodes->item(0)->parentNode->removeChild($library->childNodes->item(1));
        
    //header("Content-type: text/xml");
    $dom->save('library_modified.xml');
}

8. Delete Elements (accessed conditionally)

SimpleXML :

// Delete a book with  200<price<500
// Not possible to delete node found via XPath in SimpleXML. See below.
function fnSimpleXMLDeleteCond() {
    $library = new SimpleXMLElement('library.xml',null,true);
    $book = $library->xpath('/library/book[price>"200" and price<"500"]');
        
    // Problem here....not able to delete parent node using unset($book[0]);
    // unset of parent node only works when accessing serially. eg : unset($library->book[0]);
        
    // header("Content-type: text/xml");
    // echo $library->asXML();
    //$library->asXML('library_modified.xml');
        
}

DOM :

// Delete the book with  200<price<500 
function fnDOMDeleteCond() {
    $dom = new DOMDocument();
    $dom->load('library.xml');
    $library = $dom->documentElement;
    $xpath = new DOMXPath($dom);
    $result = $xpath->query('/library/book[price>"200" and price<"500"]');
    $result->item(0)->parentNode->removeChild($result->item(0));
    //header("Content-type: text/xml");
    $dom->save('library_modified.xml');
}

9. Rearrange / Reorder Elements

SimpleXML :

// Exchange Position of 2nd book with 3rd : fnSimpleXMLRearrange(2,3);
// Due to absence of an inbuilt function (DOM has it), we have to make our own function in SimpleXML.
//Better to use DOM.
function fnSimpleXMLRearrange($num1,$num2) {
    $libSimple= new SimpleXMLElement('library.xml',null,true);
    //$library->book[3] = $library->book[0]; // this doesnt work
  
    $libDom = dom_import_simplexml($libSimple);
 
    $dom = new DOMDocument();
    // returns a copy of the node to import
    $libDom = $dom->importNode($libDom, true);
    // associate it with the current document.
    $dom->appendChild($libDom);
 
    fnDOMRearrange($num1,$num2,$dom); // see below DOM function
}

DOM :

// Exchange Position of 2nd book with 3rd : fnDOMRearrange(2,3);
function fnDOMRearrange($num1,$num2,$dom=0) {
    if (!$dom) {
        $dom = new DOMDocument();
        $dom->load('library.xml');
    }
    $dom = new DOMDocument();
    $dom->load('library.xml');
    $library = $dom->documentElement;
    $cnt = $library->childNodes->length;
    //echo '<br> count : ' . $cnt;
 
    if ($num1 > $num2) { // ensure $num1 always is less than $num2
        $num3 = $num1;
        $num1 = $num2;
        $num2 = $num3;                      
    }
      
    $index1 = fnDOMConvIndex($num1,  $cnt);
    $index2 = fnDOMConvIndex($num2,  $cnt);
    /*for ($iter = 0; $iter <= $cnt; $iter++) {
        echo '<hr>' . $iter . '<br>' .  $library->childNodes->item($iter)->nodeValue;
    }*/
             
    $library->childNodes->item(0)->parentNode->insertBefore($library->childNodes->item($index1), $library->childNodes->item($index2)); // put x before y
    $library->childNodes->item(0)->parentNode->insertBefore($library->childNodes->item($index2), $library->childNodes->item($index1)); // put y before x 
 
    //header("Content-type: text/xml");
    $dom->save('library_modified.xml');
}

function fnDOMConvIndex($num,  $cnt) {
    // echo '<br>' . $num;
    if ($num != 1) {
        $maxIndex = floor($cnt/2);
        //echo '<br>max: ' . $maxIndex;
        if ($maxIndex == $num) {
            $num = $cnt-2;
        } else {
            $num = ($num%2)?($num+2):($num+1); // Always odd index due to nature of DOM Element Index.
        }
    }         
     
    // echo '<br>' . $num;
    return $num;
}

10. Display Required data in XML Form itself OR Remove all children nodes save one OR Copy/Clone Node Eg OR Compare/Search non numeric data (like date or time) to get result.

SimpleXML :

// Display Books published after 1980 in XML Form itself.
// No function to copy node directly in SimpleXML.
// Its simpler for this functionality to be implemented in DOM.
function fnSimpleXMLDisplayElementCond() {
    $library = new SimpleXMLElement('library.xml',null,true);
    $book = $library->xpath('/library/book[translate(@pubdate,"-","")>translate("1980-01-01","-","")]');
    // Manually create a new structure then add searched data to it (see create xml eg.)
}

DOM :

// Display Books published after 1980 in XML Form itself.
function fnDOMDisplayElementCond() {
    $dom = new DOMDocument();
    $dom->load('library.xml');
    $library = $dom->documentElement;
    $xpath = new DOMXPath($dom);
        
    // Comparing non numeric standard data
    $result = $xpath->query('/library/book[translate(@pubdate,"-","")>translate("1980-01-01","-","")]');
    // For simpler search paramater use this :
    //$result = $xpath->query('/library/book[author="J.R.R.Tolkein"]');
        
    // Copy only node & its attributes not its contents.
    $library = $library->cloneNode(false);
    // Add the 1 element which is search result.
    $library->appendChild($result->item(0));
        
    //header("Content-type: text/xml");
    $dom->save('library_modified.xml');
}

Lessons Learned

  • SimpleXML is fantastic for those who will only briefly flirt with XML (or beginners) & perform simple operations on XML.
  • DOM is an absolute necessity for performing complex operations on XML data. Its learning curve is higher than SimpleXML off course but once you get the hang of it , you will know its very logical.
  • Use XPath for conditional access to data. For serial access (like last book) XPath is not needed (but u can use it) since I can use normal DOM / SimpleXML node access.

Ref :





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